virulent

adjective4

1. •
   Of animals, plants, or substances: extremely venomous or poisonous.
2. •
   (figurative) Extremely hostile or malicious; intensely acrimonious.

   • The politicians were virulent in their hatred of the president.
3. •
   Of a disease or disease-causing agent: malignant, able to cause damage to the host.
4. •
   Of a pathogen: replicating within its host cell, then immediately causing it to undergo lysis.